Why Do Lionel Trains Have 3 Rails?

Lionel trains entertained kids of all ages for generations. These majestic model train sets even inspired a few people into engineering from train operators to mechanical and electrical engineers. While simple to operate, these trains also have seemingly questionable designs such as tracks with a third rail despite real trains requiring only two.

Model train sets such as Lionel use three-rail tracks for a variety of reasons, but most of them fall under user safety. Since the rails are the train’s power cable, the primary concern is electrical shorts frying the electronics or causing fires. As such, the third rail keeps the live power separated from the ground.

This precaution is necessary because of how Lionel trains work. By reading further, you will learn about the inner workings of Lionel trains so you can understand and better troubleshoot them. You will also learn how other model trainsets deal with the same problem.

The Reasons Lionel Trains Use 3-Rail Tracks

Lionel model trains offer hours of entertainment and education, providing the same experience as real trains but in a smaller, more manageable form. However, they have a few oddities that deviate from the real world. The third rail is one of them.

The three-track design comes from the early days of model trains. It is an unrealistic feature and a legitimate drawback for something designed to mimic the real world, but it is a required feature for any O gauge trainset. That includes Lionel Trains, though they did not start that way.

When Lionel began making model trains in 1900, there was no real standard for model trains, except for the 5-rail Marklin standard from 1891. At the time, every manufacturer had its track design, including both two and three-rail formats. Lionel was in the 2-rail camp until they released the first true, 3-rail “Standard Gauge” trains in 1906.

Advantages of Using 3-Rail Tracks

All model trainsets are simple electrical circuits. A transformer in the electrical box sends the hot signal down the hot rail. The electricity then empowers the train’s motor through its wheels. It then goes back to the transformer on the grounded rail to be sent back out of your house through the outlet.

lionel train layout
Corvair Owner

3 Rails Allow Complex Track Designs

Lionel used the center rail as the hot rail, reserving the outer two for ground. This configuration allows for complex track setups while ensuring that the circuit was simple enough for the technology of the day. A 2-rails system must reverse the polarity to avoid short circuits, which was impossible in 1906. This is the same reason many real subway systems use 3-rail tracks as well.

The Third Rail Can Act as an Automatic Switch

Through clever use of insulation, one of the rails can act as an automatic push-button switch. This setup lets the train activate crossovers, signals, and other accessories automatically as they draw near. This prevents derailments and adds a bit of realism to your models.

3-Rail Systems are the Industry Standard

Lionel’s “Standard Gauge” tracks became so popular that they became the de facto industry standard. So much so that Lionel had to keep the 3-rail design to remain compatible with preexisting accessories when they introduced the “O gauge” standard, which they would later update to the current “Super O” standard in use today. Only American Flyer used a competing 2-rail “S Gauge” standard.

3-Rails Systems Have History

Lionel’s O gauge tracks are a direct descendant of an earlier windup O gauge design. These early model train standards used only two rails but used a windup key for power. Lionel just replaced the key with electricity to produce a more automated power system, but otherwise kept its design.

Real Trains are Starting to Use 3-Rail Tracks

As mentioned before, many subway systems use 3-rail tracks as well, but even standard commuter and intercity trains are taking the plunge. As more trains come electrified, train manufacturers and operators face the same electrical issues Lionel and the model train industry faced over 100 years ago. As such, they are switching to 3-rail tracks as well, though the third rail usually hangs as a wire above the train and the main track.

How Lionel Trans Work

Three-rail systems became popular because of how model trains work. As mentioned earlier, they are simple alternating current circuits, powered by the full force of electricity coming out of the wall outlet. They use electromagnetic motors and gears to move the toy train down the track. It requires an understanding of electrical physics and engineering, but it will help understand why the third rail is usually needed.

old lionel trains

Electricity’s Journey Through Your Lionel Model Trainset

The alternating current electricity coming out of the wall outlet constantly reverses polarity. This reversal happens 60 times per second in North America and 50 in Europe. As such, it requires two live wires, a hot wire (usually black) and a return (usually white). For safety and reliability, a third wire connected to the literal ground is also present, though it is rarely used in model trains.

However, the high voltage of the household current is too unsafe for the exposed metal toy tracks. Therefore, Lionel uses a variable voltage transformer to convert the electricity into something more manageable. It also lets you change the speed of the train, giving you full control over the model.

The electricity then passes down the center rail to the motor in the train itself. After the motor, it uses the wheels to jump to the outer rails to make its journey back to the outlet, passing through the transformer one more time in the process.

The 3-Rail Setup Keeps the Circuit Simple

Because you can build your Lionel trainset to any size, the electricity will always spend most of its journey on the rails. As such, any metal placed across them will cause a short circuit. These shorts can do more harm than just prevent the train from moving. Therefore, you must take every precaution to prevent them from happening.

Lionel did some of the work for you though by using their 3-rail design. Every Lionel track component uses the same 3 rails, letting you combine them without worrying about shorting them. If linked properly, the electricity will remain going in the right direction regardless of how many switches you use.

Two-rail systems require additional equipment to do what three-rail systems do naturally. This additional equipment would then constantly reverse the polarity to ensure no shorts occur anywhere down the line. This would make the trainsets more expensive or limit the possible track layouts.

Lionel Train Motor

The Lionel motor is a collection of four electromagnetic plates with a rotating sweeper arm called a brush. The motor takes electricity through a small wire attached to a metal wheel that rests on the middle rail underneath. As the motor takes in more electricity, the arm turns faster and faster. The motor is reversible, letting you change the direction of motion with a click of a button. A series of gears transfers this motion to the main wheels.

The entire structure only works as-is with three-rail tracks. As such, Lionel would need to recreate their century’s worth of transects if they wanted to change the gauge of the tracks. Even the gear shift, a solenoid that reacts to power changes, requires the third rail to function. Therefore, it is very unlikely that the brand will ever change the structure of its 3-rail tracks.

Differences between Lionel and other Model Trains

As most fans prefer the 3-rail tracks, there is no incentive for Lionel to change things now. Luckily, some of the other model train manufacturers use different gauge tracks. As such, we have a way to compare current Lionel with how they would look and function with a 2-rail system. In particular, we can use American Flyer trains.

As mentioned earlier, American Flyer invented the current 2-rail standard as an alternative to Lionel’s 3-rail design. This decision affected how they designed their trainsets, making them incompatible with each other. These issues would persist even if you modified the tracks to accommodate the other’s system. Some of the more notable differences are as follows.


Lionel focuses on the toy train market. American Flyer does scale modeling. These foci affected their choice of rail gauge in the early 1900s, including Flyer’s switch to the 2-rail S gauge track system. This allowed Flyer to produce more accurate scale models of real trains.

This scalability lets Flyer produce model trains of any size, allowing for some incredibly detailed trains. It also allowed Flyer trains to get ridiculously small requiring much smaller operating spaces than the consistent 1:64-scale Lionel train sets. But it also reduces the complexity and number of available accessories, which had to be equally as small to compensate.

Lionel trains may require more space, but you know everything would be consistent. You will never have to consider if an accessory is too big or too small for your Lionel trainset. It will just fit as-is. Lionel would reduce their production costs with a 2-rail train, but at the cost of user imagination.

lionel trains
Marine 69-71


Track design is probably the first difference people notice when comparing model trainsets with the biggest difference being the number of rails. As mentioned before, all modern model trainsets generally fall under just two standard track styles:

  • O Gauge: a three-track design led by Lionel
  • S Gauge: a two-track design led by American Flyer

Though, you may also find a few train kits that still use the old 3-rail Standard Gauge.

S gauge offers a more realistic design, but it does come with a major design flaw. For instance, S gauge tracks cannon have reverse loops without shorting out. Reverse loops are circular tracks that let the train make a U-turn and go in the opposite direction.

With O gauge, all the power runs down the center rail. This setup keeps the hot and return lines separated, avoiding the risk of the short circuit entirely. Plus, it is the more traditional design, serving as a direct descendant of a much older windup-up train design.


One advantage O trains have is their streamlined power supply. Lionel trains can use AC power directly. That means they can use smaller, safer, and less complicated transformers. The tracks are live when in operation, but the system costs less to build and maintain, which they passed on to their consumers through cheaper prices and full control over the train’s speed.

On the other hand, S trains run on DC power. DC makes the rails safer to handle, but it leads to slower trains. They also require specialized transformers called converters to operate properly. These “rectiformers’, as they are often called, are noticeably bigger than pure AC units, making them more cumbersome to use and expensive.


Couplers connect the trains to their cars and other rolling stock. Every model train company went through numerous incompatible coupler designs before they settled on today’s semi-automatic coupling system. Similar to their real-world counterparts, these model couplers could couple and decouple via remote controls.

Their main difference was how the remote control worked:

  • Lionel and other O-type trains use electronic couplers
  • American Flyer uses a mechanical uncoupling device.

Both systems received minor updates over the years until Lionel introduced the current, more realistic knuckle coupler. While looking like the Flyer’s decoupler, the Lionel version used magnets to couple and decouple cars, allowing their system to be completely controlled remotely.

You can also operate them like real trains and have them connect just by slowly bringing the two couplers to close. The magnets inside will do the rest.

Lionel is the Only One the Remains

The final difference between the two model train standards is that Lionel won. Both Lionel and American Flyer failed and were bought out by General Mills in the mid-60s, who would later spin them off as their own company. Today, this new Lionel company owns and makes both brands to maintain compatibility with preexisting stock and the needs of their customers.


Lionel model trains offer a fantastic way to enjoy the majesty of trains in your home. However, they use a 3-rail track system that appears to be at odds with the realism of their trains. This track system exists due to how Lionel trains operate and the benefits it provides.



Lifelong Rail Enthusiast and Owner of Worldwide Rails

Recent Posts